Table7_Supplementation of serum albumin is associated with improved pulmonary function: NHANES 2013–2014.DOCX

Background: The serum albumin level is reflective of the function of multiple organs, such as the liver and kidneys. However, the association between serum albumin and pulmonary function is unclear; therefore, this study aimed to determine the relationship between pulmonary function and serum albumin, including the threshold of serum albumin at the changes of the pulmonary function in the total population and in different strata of population.
Methods: In this cross-sectional study, We examined the relationship between serum albumin and two independent indicators of pulmonary function: forced vital capacity (FVC) and forced expiratory volume in one second (FEV 1), using data from National Health and Nutrition Examination Survey (NHANES 2013–2014) (n = 3286). We used univariate analysis, stratified analysis, and multiple regression equation analysis to examine the correlation between serum albumin levels and FVC and FEV 1, and performed smoothed curve fitting, threshold effect, and saturation effect analysis (for stratification) to determine the threshold serum albumin level at which FVC and FEV 1 begin to change.
Results: The adjusted smoothed curve fit plot showed a linear relationship between serum albu-min levels and FVC: for every 1 g/dl increase in the serum albumin level, FVC increased by 80.40 ml (11.18, 149.61). Serum albumin and FEV 1 showed a non-linear relationship. When serum al-bumin reached the inflection point (3.8 g/dl), FEV 1 increased with increasing serum albumin and the correlation coefficient β was 205.55 (140.15, 270.95).
Conclusion: Serum albumin is a core indicator of liver function, and abnormal liver function has a direct impact on pulmonary function. In the total population, serum albumin levels were linearly and positively correlated with FVC. Above 3.6 g/dl, serum albumin was positively correlated with FEV 1. Based on the total population and different population strata, this study revealed a positive association between the serum albumin level and pulmonary function, and identified the threshold of serum albumin when Indicators of pulmonary function tests starts to rise, providing a new early warning indicator for people at high risk of pulmonary insufficiency and has positive implications for the prevention of combined respiratory failure in patients with liver insufficiency.

背景：血清白蛋白水平可反映肝脏、肾脏等多个脏器的功能状态。然而目前血清白蛋白与肺功能之间的关联尚不明确，因此本研究旨在明确全人群及不同人口分层人群中，肺功能与血清白蛋白的关联，并探究肺功能发生变化时对应的血清白蛋白阈值。
方法：本研究为横断面研究，采用2013-2014年美国国家健康与营养检查调查（National Health and Nutrition Examination Survey, NHANES 2013–2014）的数据（n=3286），分析血清白蛋白与两项肺功能独立指标——用力肺活量（forced vital capacity, FVC）及一秒用力呼气容积（forced expiratory volume in one second, FEV1）之间的关联。研究采用单因素分析、分层分析及多元回归方程分析，探讨血清白蛋白水平与FVC、FEV1的相关性，并通过平滑曲线拟合、阈值效应及饱和效应分析（用于分层研究），明确FVC与FEV1开始发生变化时对应的血清白蛋白阈值。
结果：校正后的平滑曲线拟合图显示，血清白蛋白水平与FVC呈线性相关：血清白蛋白每升高1g/dl，FVC增加80.40ml（95%置信区间：11.18, 149.61）。血清白蛋白与FEV1则呈非线性相关。当血清白蛋白达到拐点（3.8g/dl）时，FEV1随血清白蛋白水平升高而增加，相关系数β为205.55（95%置信区间：140.15, 270.95）。
结论：血清白蛋白是肝功能的核心指标，肝功能异常可直接影响肺功能。在全人群中，血清白蛋白水平与FVC呈线性正相关；当血清白蛋白水平高于3.6g/dl时，其与FEV1呈正相关。本研究基于全人群及不同人口分层人群，明确了血清白蛋白水平与肺功能呈正相关关系，并确定了肺功能检测指标开始升高时对应的血清白蛋白阈值，可为肺功能不全高危人群提供新型早期预警指标，同时对预防肝功能不全患者合并呼吸衰竭具有积极意义。